The present invention relates to a television receiver which is provided with functional boards having different functions such as the functions of television tuners for different color television systems, the function of a teletext demodulator (namely, demodulator for teletext), and the function of a satellite broadcast wave receiver (namely, demodulator for received satellite broadcast wave).
In order to satisfy various needs of users, it is necessary for a conventional television receiver to have a structure applicable to many kinds of receivers. For example, the conventional television receiver is required to have a structure applicable for a television receiver having a built-in satellite broadcast wave receiver, a television receiver having a built-in teletext receiver, a television receiver having both a built-in satellite broadcast wave receiver and a built-in teletext receiver, and television receivers for different color television systems such as NTSC,
and SECAM.
In order to satisfy the above requirement, a television receiver uses a fundamental model applicable for many kinds of television receivers, and has a structure shown in FIG. 3. In FIG. 3, reference numeral 1 designates a speech processing circuit, 2 a video signal changeover circuit, 3 a satellite broadcast were receiver, 4 a television tuner, 5 a VIF circuit, 6 a teletext demodulator, 7 a video/chroma/deflection processing circuit, 8 an FBT (fly back transformer), and 9 a microcomputer. The speech processing circuit 1, the video signal changeover circuit 2, the television tuner 4, the VIF circuit 5, the video/chroma/deflection processing circuit 7, the FBT 8, the microcomputer 9, and a power circuit are mounted on a printed wiring board 11 of a television receiver, to be connected to one another. Further, these circuits and parts are connected to a CRT 13 mounted on an outer cabinet 12, to perform the fundamental operation of the television receiver. Additionally, the satellite broadcast wave receiver and the teletext demodulator 6 are fixed to side faces of speakers 14a and 14b mounted on the outer cabinet 12, respectively, and are connected to the printed wiring board 11 through lead wires 15 and connectors 16.
When such a television receiver is produced, it is necessary for the microcomputer 9 to check whether or not each of the satellite broadcast wave receiver 3 and the teletext demodulator 6 has been attached to the television receiver. A method of judging whether each of the parts 3 and 6 is present or not, will be explained below, with reference to the block diagram shown in FIG. 4.
Referring to FIG. 4, control signals stored previously in the memory of the microcomputer 9 are sent to circuit blocks, to control the circuit blocks, thereby causing the television receiver to function. In order to check whether or not each of the teletext demodulator 6 and the satellite broadcast wave receiver 3 is included in the television receiver, a series combination of a resistor 21 and a jumper wire 22 and a series combination of a resistor 23 and a jumper wire 24 are both connected between a power source 20 and a ground, and an electric potential at the connecting point between the resistor 21 or 23 and the jumper wire 22 or 24 is detected by the microcomputer 9. In more detail, in a case where the jumper wire 22 is absent, a lead wire 25 connected to the resistor 21 has the potential of the power source 20, and it is judged by the microcomputer 9 that the teletext demodulator 6 is incorporated in the television receiver. Hence, the microcomputer 9 controls the function of the teletext demodulator 6. In contrast to the above, in a case where the jumper wire 22 is present, the lead wire 25 connected to the resistor 21 has a ground potential, and it is judged by the microcomputer 9 that the teletext demodulator 6 is not incorporated in the television receiver. Hence, the microcomputer 9 controls the function of the television receiver devoid of the teletext demodulator 6.
Similarly, the presence and absence of the satellite broadcast wave receiver 3 correspond to the absence and presence of the jumper wire 24, respectively, and it is judged on the basis of the potential of a lead wire 26 connected to the resistor 23 whether or not the satellite broadcast wave receiver 3 is included in the television receiver. In order to fabricate four kinds of television receivers board upon the above combinations, it is required that four kinds of printed wiring boards based upon the presence of absence of each of two jumper wires are produced and managed in a factory. Further, the teletext demodulator 6 and the satellite broadcast wave receiver 3 are selectively attached to the television receivers in accordance with four kinds of printed wiring boards. Then, the functions of the teletext demodulator 6 and the satellite broadcast wave receiver 3 are checked, and the television receivers thus obtained are managed.